Inactivating and mutagenic effects of nitrosoguanidine on simian virus 40

N-methyl-N'-nitro-N-nitrosoguanidine (NTG) in high concentrations inactivates extracellular simian virus 40. No mutants were found in stocks of virions partially inactivated by NTG under the experimental conditions employed. In contrast, NTG in low concentrations inhibits the intracellular replication of simian virus 40 and is an effective mutagen of the intracellular virus. Six temperature-sensitive mutants of simian virus 40 have been isolated for genetic studies of the virus and its interaction with mammalian cells.